Production of acetylene



United States Patent 6 Claims. (51. 260-679) This invention relates to an improved process for producing acetylene.

It is known that acetylene can be produced by thermal conversion of hydrocarbons, for example by partial oxidation of hydrocarbons (particularly methane or light naphtha) with oxygen in a flame reaction. The cracked gas containing about 10% of acetylene which is at a temperature of about 1500" C. must be cooled very rapidly and the conventional way of achieving this is by spraying in a suitable liquid.

It is also known that hot cracked gas containing acetylene may be quenched with water. The use of water has the disadvantage however that the heat given up by the hot cracked gas cannot be utilized and is thus lost.

It is furthermore known that the cracked gas contain ing acetylene may be quenched with high boiling point aromatic hydrocarbon oils. In this way it is possible to make use of the whole of the heat energy contained in the cracked gas and to remove the carbon black from the gas in a simple and effective way. In general there is no appreciable cracking of the high boiling point aromatic hydrocarbon oil in the said process. If however the hydrocarbon oil is freed from carbon black and then used again as a quenching liquid, and this process is carried out repeatedly, some of the constituents of the hydrocarbon oil are gradually converted into asphalts or carbon black and part of the sulfur contained in the hydrocarbon oils is converted into hydrogen sulfide which causes corrosion in the pipes and equipment. Another disadvantage is that the conventional hydrocarbon oils do not quench the hot cracked gas as rapidly, intensely and uniformly as water. If acetylene remains too long in the region of high temperature, however, it decomposes into carbon black and hydrogen so that the acetylene yield decreases whereas the undesirable formation of carbon black increases. A further disadvantage is that the hydrocarbon oils, which are obtainable commercially for example as fuel oils, have greatly differing compositions and therefore different properties. For this reason each hydrocarbon oil must be thoroughly investigated prior to use, and this is not only time-consuming but also expensive.

We have now found that the abovementioned disadvantages do not occur when naphthalene or an a-halonaphthalene is used as the aromatic hydrocarbon oil.

It has been found that when hot cracked gas at about 1500 C. is quenched in a single stage to about 200 C. no undesirable decomposition of acetylene takes place and the cracked gas has the same composition as when water is used as the quenching liquid. The fact that the thermal stability of naphthalene is considerably greater than that of other high boiling point aromatic hydrocarbon oils is a particular advantage.

Naphthalene is 3,287,435 Patented Nov. 22, 1966 ice therefore particularly well suited for a regeneration process, i.e. a portion of the naphthalene may be continually withdrawn from the liquid cycle and freed from carbon black. The naphthalene freed from carbon black is used again for quenching either alone or mixed with naphthalene containing carbon black. It is advantageous to free just suflicient naphthalene from carbon black to ensure that a constant content of carbon black is maintained in the recycled naphthalene, for example at a level of 10 to 30%, particularly 20%. p

The risk of corrosion of the equipment and pipes through which the product flows after the cracked gas has been quenched is considerably less because naphthalene, contrasted with other hydrocarbon oils, is free from sulfur. It is quite a special advantage of the process according to this invention that naphthalene is a defined chemical substance and as such is obtainable always in the same quality.

The portion of the naphthalene which evaporates during the quenching is advantageously condensed in a conventional way in a column by means of a low boiling point aromatic hydrocarbon oil and passed through the bottom of the column to the quenching zone in .a chemically unchanged form, while the light hydrocarbon oil evaporates, is condensed in a condenser and separated from water in a separating vessel. There are no deposits or incrustations in the condensation column, even after prolonged periods of operation, whereas when using aromatic oils as quenching liquids, the lower portion of the column becomes soiled and this may lead to interruptions in the operation. The portion of naphthalene which remains liquid during quenching is advantageously united with the other naphthalene separated from cracked gas in the above-mentioned column, and the heat given up by the gas and contained in the naphthalene may be reused for any desired purpose, for example for the production of steam. Naphthalenes having a halogen atom as substituent in a-position, as for example a-chloronaphthalene, have the same advantageous properties as naphthalene itself.

The invention is illustrated by the following example which shows the advantages associated with the process.

Example 370 kg. per hour of gasoline is heated to 350" C. in a preheater and 250 cubic meters (S.T.P.) of oxygen per hour is preheated to 350 C. in a second preheater. The mixture is converted into cracked gas containing acetylene in a combustion chamber. At the outlet from the combustion chamber, the hot cracked gas is quenched in one case with a high boiling point aromatic oil and in another case with naphthalene. The cracked gas at 180 C. which has been quenched with the aromatic oil contains 9.5% by volume of acetylene and mg. of hydrogen sulfide per cubic meter (S.T.P.) and that which has been quenched with naphthalene contains 9.9% by volume of acetylene and 40 mg. of hydrogen sulfide per cubic meter (S.T.P.).

We claim:

1. A process for the production of acetylene from hydrocarbons by the action of high temperatures, quenching the hot cracked gas containing acetylene and separating carbon black from the gas with an aromatic hydrocarbon oil, wherein a member selected from the group consisting of naphthalene and an a-halonaphthalene is used as the aromatic hydrocarbon oil.

2. A process as claimed in claim 1 wherein a portion of the naphthalene containing carbon black is freed from carbon black and the naphthalene freed from carbon black is used again for quenching.

3. A process as claimed in claim 1 wherein the naphthalene vapors entrained with the quenched gas are condensed by means of a low boiling point hydrocarbon oil.

4. A process as claimed in claim 3 wherein the low boiling point hydrocarbon oil is free from polymerizable substances.

5. A process as claimed in claim 1 wherein the heat transmitted to thenaphthalene is utilized.

References Cited by the Examiner UNITED STATES PATENTS 2,371,147 3/1945 Burk 339-083 2,394,848 2/ 1946 Doumani 26 0 6-79 2,597,346 5/ 1952 Lei-fer 260679 3,140,323 7/ 1964 Fauser 260-679 15 ALPHONSO D. SULLIVAN, Primary Examiner. 

1. A PROCESS FOR THE PRODUCTION OF ACETYLENE FROM HYDROCARBONS BY THE ACTION OF HIGH TEMPERATURES, QUENCHING THE HOT CRACKED GAS CONTAINING ACETYLENE AND SEPARATING CARBON BLACK FROM THE GAS WITH AN AROMATIC HYDROCARBON OIL, WHEREIN MEMBER SELECTED FROM THE GROUP CONSISTING OF NAPHTHALENE AND AN A-HALONAPHTHALENE IS USED AS THE AROMATIC HYDROCARBON OIL. 